Over 80,000 chemicals are in use in the United States and over 2,000 new ones are introduced annually (NRC, 1984; OTA, 1995). While relatively few of these chemicals are likely to pose a significant risk to human health or the environment, the effects of most of them are unknown. Of particular concern, particularly in children, are those that may affect the endocrine system. The potential health significance of endocrine disruptors that act through peroxisome proliferator- activated receptors (PPARs) is receiving more attention. Many of these are found at significant levels in infants and children and have the potential of influencing metabolic disorders including obesity, diabetes, chronic inflammatory diseases and cardiovascular disease. In vitro screening tests to identify PPAR agonists currently available measure receptor binding or whole genome expression. These assays are clearly informative but the former provides no information on biological activities and the latter lacks specificity and can be difficult to translate to human health effects, having limied portability of the required technology to clinical studies and requiring intensive statistical analyses. Furthermore, PPAR responses are complex and difficult to interpret in terms of causality. PPAR-dependent responses are not only extremely diverse, but occur in both a species- and tissue-specific manner. The response can be influenced by the agonist concentration and combinations thereof as well as specific binding affinities. Given these current limitations, we propose to establish a high throughput in vitro cell culture screening assay to identify gene expression changes in key biological pathways that occur from putative environmental PPAR agonists using a low-density focused array card and selected human cell lines including HepaRG and THP1 cells, (hepatocyte and monocytes cell lines, respectively). Previous published studies and preliminary data provided here suggests that these cell lines respond to activation by PPAR agonists, reflect the biological responses that occur following human exposures and provide sufficient sensitivity indicating a high likelihood for success. The focus of this hypothesis-driven testing scheme is to identify agonists that can potentially produce health effects related to metabolic disorders such as hypercholesterolemia, obesity, type 2 diabetes and chronic inflammatory diseases. Results from these studies will help identify endocrine disruptors that have the potential to affect human health through their ability to serve as PPAR agonists. It can also be used to identify specific and potent candidate therapeutics for the treatment of metabolic disorders.